Years ago, I needed a coil swapped. Most of the refrigerant was still in the system. The tech recovered it. Then tried to charge me for putting it back in! I called BS and refused to pay. Eventually, he owned up and told me the system took 3 pounds. Then I made him eat those as the repair was warranty and would not of leaked out if the part had not been defective. Still gave me grief right up until I offered to call the manufacturer and complain.
Unless the warranty specifically excludes refrigerant, it is part of the warranty job. In the autmotive world, warranties will specifically exclude oil and coolant in warranty repairs and most dealers will eat those costs as good will. The driving force behind the OEM not covering fluids is dealers do not buy OEM coolant or oil and instead, bulk purchase from a local supplier.
I've a neighbor who owns a large site preparation company. He will go in, clear 10 acres, excavate for the office building foundation, level parking lots, prep with rock and crushNrun. Part of the job entails removing a lot of top soil to shape the property. He charges for that. Mounds it in the corner of the site. Then fill is needed to bring areas up to grade. He takes from 'his pile' and charges for that. At the end of the job, he sells the pile off. Double and triple bills for the same dirt. Apparently, an accepted practice.